The sub-tropical high pressure belts extend from the tropics to about 350 latitudes in both the Hemispheres.
In the northern hemisphere it is called as the North sub-tropical high pressure belt and in the southern hemisphere it is known as the South sub-tropical high pressure belt.
The existence of these pressure belts is due to the fact that the uprising air of the equatorial region is deflected towards poles due to the earth’s rotation.
After becoming cold and heavy, it descends in these regions and gets piled up.
This results in high pressure.
Calm conditions with feeble and variable winds are found here.
In olden days vessels with cargo of horses passing through these belts found difficulty in sailing under these calm conditions.
They used to throw the horses in the sea in order to make the vessels lighter.
Henceforth these belts or latitudes are also called ‘horse latitudes’.
These are the regions of divergence because winds from these areas blow towards equatorial and sub-polar low pressure belts.